System and method for reducing current exiting a roll through its bearings

ABSTRACT

A system includes a roll formed from a conductive material, where the roll is configured to rotate about an axis. The system also includes an induction heating workcoil configured to generate currents within the roll. The induction heating workcoil is unbalanced and is oriented so that minimal currents flow in a direction substantially parallel to the axis of the roll. The induction heating workcoil could include one or more substantially U-shaped or C-shaped cores and at least one coil each wound around at least one of the one or more cores. Also, the roll may further include a shaft and bearings, and the induction heating workcoil can be positioned so that the currents do not flow substantially through the bearings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure is related to the following U.S. patent applications,which are incorporated by reference:

Ser. No. ______ entitled “SYSTEM AND METHOD FOR REDUCING CURRENT EXITINGA ROLL THROUGH ITS BEARINGS USING BALANCED MAGNETIC FLUX VECTORS ININDUCTION HEATING APPLICATIONS” filed on ______ [DOCKET NO.H0019204-0108]; and

Ser. No. ______ entitled “SYSTEM, APPARATUS, AND METHOD FOR INDUCTIONHEATING USING FLUX-BALANCED INDUCTION HEATING WORKCOIL” filed on ______[DOCKET NO. H0019526-0108].

TECHNICAL FIELD

This disclosure relates generally to paper production systems and othersystems using rolls. More specifically, this disclosure relates to asystem and method for reducing current exiting a roll through itsbearings.

BACKGROUND

Paper production systems and other types of systems often include anumber of large rotating rolls. For example, sets of counter-rotatingrolls can be used in a paper production system to compress a paper sheetbeing formed. The amount of compression provided by the counter-rotatingrolls is often controlled through the use of induction heating devices.The induction heating devices create currents in a roll, which heats thesurface of the roll. The heat or lack thereof causes the roll to expandand contract, which controls the amount of compression applied to thepaper sheet being formed.

SUMMARY

This disclosure provides a system and method for reducing currentexiting a roll through its bearings.

In a first embodiment, a system includes a roll formed from a conductivematerial, where the roll is configured to rotate about an axis. Thesystem also includes an induction heating workcoil configured togenerate currents within the roll. The induction heating workcoil isunbalanced and is oriented so that minimal currents flow in a directionsubstantially parallel to the axis of the roll.

In particular embodiments, the induction heating workcoil includes oneor more U-shaped or C-shaped cores and at least one coil each woundaround at least one of the one or more cores.

In other particular embodiments, the roll further includes a shaft andbearings. Also, the induction heating workcoil is oriented so that thecurrents do not flow substantially through the bearings.

In yet other particular embodiments, the roll represents one of a set ofcounter-rotating rolls. The counter-rotating rolls are configured tocompress a web of material. Also, an induction heating actuator includesthe induction heating workcoil and a power source coupled to at leastone coil of the induction heating actuator. In addition, the systemfurther includes a controller configured to control the power source tocontrol an amount of compression provided by at least a portion of thecounter-rotating rolls.

In still other particular embodiments, multiple induction heatingworkcoils are located adjacent to each other in a row proximate to theroll. Also, multiple rows of induction heating workcoils are locatedadjacent to each other proximate to the roll.

In a second embodiment, a system includes a roll formed from aconductive material, where the roll is configured to rotate about anaxis. The system also includes an induction heating workcoil configuredto generate a magnetic flux for producing currents within the roll. Theinduction heating workcoil is unbalanced and is oriented so that a pathof the magnetic flux through the roll is substantially parallel to theaxis of the roll.

In a third embodiment, a method includes placing an induction heatingworkcoil in proximity with a roll. The roll is configured to rotateabout an axis, and the induction heating workcoil represents anunbalanced induction heating workcoil. The method also includesorienting the induction heating workcoil so that a magnetic flux pathwithin the roll produced by the induction heating workcoil is axiallyaligned with the axis of the roll. In addition, the method includesproducing currents within the roll.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an example paper production system according to thisdisclosure;

FIGS. 2A and 2B illustrate example orientations of an induction heatingworkcoil with respect to a roll according to this disclosure;

FIG. 3 illustrates an example configuration of induction heatingworkcoils with respect to a roll according to this disclosure; and

FIG. 4 illustrates an example method for reducing current exiting a rollthrough its bearings according to this disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 4, discussed below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the invention. Those skilled in the art willunderstand that the principles of the invention may be implemented inany type of suitably arranged device or system.

FIG. 1 illustrates an example paper production system 100 according tothis disclosure. The embodiment of the paper production system 100 shownin FIG. 1 is for illustration only. Other embodiments of the paperproduction system 100 may be used without departing from the scope ofthis disclosure.

As shown in FIG. 1, the paper production system 100 includes a papermachine 102, a controller 104, and a network 106. The paper machine 102includes various components used to produce a paper product. In thisexample, the various components may be used to produce a paper web orsheet 108 collected at a reel 110. The controller 104 monitors andcontrols the operation of the system 100, which may help to maintain orincrease the quality of the paper sheet 108 produced by the papermachine 102.

In this example, the paper machine 102 includes a headbox 112, whichdistributes a pulp suspension uniformly across the machine onto acontinuous moving wire screen or mesh 113. The pulp suspension enteringthe headbox 112 may contain, for example, 0.2-3% wood fibers, fillers,and/or other materials, with the remainder of the suspension beingwater. The headbox 112 may include an array of dilution actuators, whichdistributes dilution water or a suspension of different composition intothe pulp suspension across the sheet. The dilution water may be used tohelp ensure that the resulting paper sheet 108 has a more uniform basisweight or more uniform composition across the sheet 108. The headbox 112may also include an array of slice lip actuators, which controls a sliceopening across the machine from which the pulp suspension exits theheadbox 112 onto the moving wire screen or mesh 113. The array of slicelip actuators may also be used to control the basis weight of the paperor the distribution of fiber orientation angles of the paper across thesheet 108.

An array of drainage elements 114, such as vacuum boxes, removes as muchwater as possible. An array of steam actuators 116 produces hot steamthat penetrates the paper sheet 108 and releases the latent heat of thesteam into the paper sheet 108, thereby increasing the temperature ofthe paper sheet 108 in sections across the sheet. The increase intemperature may allow for easier removal of additional water from thepaper sheet 108. An array of rewet shower actuators 118 adds smalldroplets of water (which may be air atomized) onto one or both surfacesof the paper sheet 108. The array of rewet shower actuators 118 may beused to control the moisture profile of the paper sheet 108, reduce orprevent over-drying of the paper sheet 108, correct any dry streaks inthe paper sheet 108, or enhance the effect of subsequent surfacetreatments (such as calendering).

The paper sheet 108 is then often passed through a calender havingseveral nips of counter-rotating rolls 119. Arrays of induction heatingworkcoils 120 heat the surfaces of various ones of these rolls 119. Aseach roll surface locally heats up, the roll diameter is locallyexpanded and hence increases nip pressure, which in turn locallycompresses the paper sheet 108 and transfers heat energy to it. Thearrays of induction heating workcoils 120 may therefore be used tocontrol the caliper (thickness) profile of the paper sheet 108. The nipsof a calender may also be equipped with other actuator arrays, such asarrays of air showers or steam showers, which may be used to control thegloss profile or smoothness profile of the paper sheet.

Two additional actuators 122-124 are shown in FIG. 1. A thick stock flowactuator 122 controls the consistency of the incoming stock received atthe headbox 112. A steam flow actuator 124 controls the amount of heattransferred to the paper sheet 108 from drying cylinders 123. Theactuators 122-124 could, for example, represent valves controlling theflow of stock and steam, respectively. These actuators may be used forcontrolling the dry weight and moisture of the paper sheet 108.Additional components could be used to further process the paper sheet108, such as a supercalender (for improving the paper sheet's thickness,smoothness, and gloss) or one or more coating stations (each applying alayer of coatant to a surface of the paper to improve the smoothness andprintability of the paper sheet). Similarly, additional flow actuatorsmay be used to control the proportions of different types of pulp andfiller material in the thick stock and to control the amounts of variousadditives (such as retention aid or dyes) that are mixed into the stock.

This represents a brief description of one type of paper machine 102that may be used to produce a paper product. Additional detailsregarding this type of paper machine 102 are well-known in the art andare not needed for an understanding of this disclosure. Also, thisrepresents one specific type of paper machine 102 that may be used inthe system 100. Other machines or devices could be used that include anyother or additional components for producing a paper product. Inaddition, this disclosure is not limited to use with systems forproducing paper sheets and could be used with systems that process thepaper sheets or with systems that produce or process other products ormaterials in continuous webs (such as plastic sheets or thin metal filmslike aluminum foils).

In order to control the paper-making process, one or more properties ofthe paper sheet 108 may be continuously or repeatedly measured. Thesheet properties can be measured at one or various stages in themanufacturing process. This information may then be used to adjust thepaper machine 102, such as by adjusting various actuators within thepaper machine 102. This may help to compensate for any variations of thesheet properties from desired targets, which may help to ensure thequality of the sheet 108.

As shown in FIG. 1, the paper machine 102 includes a scanner 126, whichmay include one or more sensors. The scanner 126 is capable of scanningthe paper sheet 108 and measuring one or more characteristics of thepaper sheet 108. For example, the scanner 126 could include sensors formeasuring the weight, moisture, caliper (thickness), gloss, color,smoothness, or any other or additional characteristics of the papersheet 108. The scanner 126 includes any suitable structure or structuresfor measuring or detecting one or more characteristics of the papersheet 108, such as sets or arrays of sensors.

The controller 104 receives measurement data from the scanner 126 anduses the data to control the system 100. For example, the controller 104may use the measurement data to adjust the various actuators in thepaper machine 102 so that the paper sheet 108 has properties at or neardesired properties. The controller 104 includes any hardware, software,firmware, or combination thereof for controlling the operation of atleast part of the system 100. Also, while one controller is shown here,multiple controllers could be used to control the paper machine 102.

The network 106 is coupled to the controller 104 and various componentsof the system 100 (such as actuators and scanners). The network 106facilitates communication between components of system 100. The network106 represents any suitable network or combination of networksfacilitating communication between components in the system 100. Thenetwork 106 could, for example, represent an Ethernet network, anelectrical signal network (such as a HART or FOUNDATION FIELDBUSnetwork), a pneumatic control signal network, or any other or additionalnetwork(s).

In one aspect of operation, the induction heating workcoils 120 mayoperate by generating currents in the surface of one or more of therolls 119. In some conventional systems, the currents created in a rollcan exit the roll through its bearings. These so-called “bearingcurrents” (also called “shaft currents”) can lead to premature wear anddamage to the bearings supporting the roll. For example, the bearingscan sometimes separate by small distances, and the currents flowingthrough the bearings can create sparks that pit or otherwise damage thebearings. Because of this, the bearings need to be replaced sooner ormore often than desired. This leads to down time of the system 100 andmonetary losses. While insulated bearings are available and could beused, the insulated bearings are often quite expensive compared toconventional bearings. In accordance with this disclosure, the inductionheating workcoils 120 are configured so that little or no current flowsout of the rolls 119 through their bearings. This leads to reduced wearon and damage to the bearings, resulting in increased usage and fewerreplacements. Additional details are provided below.

Although FIG. 1 illustrates one example of a paper production system100, various changes may be made to FIG. 1. For example, other systemscould be used to produce paper sheets or other products. Also, whileshown as including a single paper machine 102 with various componentsand a single controller 104, the production system 100 could include anynumber of paper machines or other production machinery having anysuitable structure, and the system 100 could include any number ofcontrollers. In addition, FIG. 1 illustrates one operational environmentin which induction heating workcoils 120 or other workcoils can be usedand oriented to reduce currents flowing through bearings of one or morerolls. This functionality could be used in any other suitable system.

FIGS. 2A and 2B illustrate example orientations 200 a-200 b of aninduction heating workcoil with respect to a roll according to thisdisclosure. In the example shown in FIG. 2A, an induction heatingworkcoil 202 includes at least one coil 204 and a core 206. The coil 204generally represents any suitable conductive material(s) wound in a coilor otherwise wrapped around at least a portion of the core 206. The coil204 could, for example, represent Litz wire or other conductive wirewrapped around the core 206. The core 206 generally represents astructure that can direct or focus a magnetic field created by currentflowing through the coil 204. The core 206 could, for example, representferrite. Terminal wires 208 couple the coil 204 to a power source 210,forming an induction heating actuator. The power source 210 generallyrepresents a source of electrical energy flowing through the coil 204.The power source 210 could, for example, represent an alternatingcurrent (AC) source that operates at a specified frequency (such as 16kHz or other frequency). The AC signal flows through the coil 204 andproduces a magnetic flux 212.

In this example, the induction heating workcoil 202 is placed inproximity to a roll 214. The magnetic flux 212 produces currents 216that flow through the surface of the roll 214, heating the surface ofthe roll 214. The production of the currents 216 can be adjusted tocontrol the amount of heating of the roll's surface, which also controlsthe amount of compression applied by the roll 214 to a paper sheet orother product.

In this embodiment, the induction heating workcoil 202 represents anunbalanced workcoil, meaning the workcoil 202 produces magnetic fluxesthat have an appreciably non-null sum spatial vector. In other words,for an individual workcoil 202 or collection of workcoils 202, theworkcoil(s) 202 can produce enough current to damage the bearings of theroll 214.

As shown in FIG. 2A, the currents 216 produced by the induction heatingworkcoil 202 flow generally perpendicular to the path of the inducedmagnetic flux 212. However, in this orientation 200 a, the path of themagnetic flux 212 is substantially orthogonal (perpendicular) to an axis218 about which the roll 214 rotates. Because of this, the currents 216flow in a direction that is generally parallel to the axis 218 of theroll 214. As a result, in this orientation 200 a, the currents 216 wouldtherefore exit the roll 214 through bearings supporting the roll 214 atthe ends of the roll 214.

As shown in FIG. 2B, the induction heating workcoil 202 has beenrepositioned so that the path of the induced magnetic flux 212 withinthe roll 214 is generally parallel to or axially aligned with the axis218 about which the roll 214 rotates. Again, the currents 216 producedby the induction heating workcoil 202 flow generally perpendicular tothe path of the induced magnetic flux 212. Here, though, the currents216 flow in a direction that is generally orthogonal to the roll axis218. More specifically, the currents 216 produced by the inductionheating workcoil 202 flow in a direction normal to the roll axis 218(rather than towards the ends of the roll 214). In this way, little ornone of the currents 216 may flow through the bearings at the ends ofthe roll 214. It may be noted that the induction heating workcoil 202could initially be installed (and possibly even used for a period oftime) as shown in FIG. 2A and then reoriented as shown in FIG. 2B. Theability to reorient the induction heating workcoil 202 may be associatedwith the workcoil alone, mounting hardware used to mount the workcoil, asupport beam on which the workcoil is mounted, a combination of thesestructures, or any other suitable structure(s).

Although FIGS. 2A and 2B illustrate examples of orientations 200 a-200 bof an induction heating workcoil with respect to a roll, various changesmay be made to FIGS. 2A and 2B. For example, any suitable number ofinduction heating workcoil 202 could be used with the roll 214. Also, inthe example shown in FIGS. 2A and 2B, the induction heating workcoil 202includes an open substantially U-shaped core 206 having opposed legs anda central portion, and the coil 204 is formed around the central portionof the core 206. Here, the U-shape is defined by a cross-section of thecore 206 lengthwise along the legs and through the central portion ofthe core 206. The core 206 could have any other suitable shape orcross-section (such as a substantially C-shaped core), and one ormultiple coils 204 could be placed in any suitable location(s) on thecore 206. As a particular example, one or more coils 204 could be placedon each opposed leg of the U-shaped core 206. In general, any inductionheating workcoil 202 that can create an induced magnetic flux that issubstantially axially aligned with or parallel to the axis 218 of theroll 214 could be used here.

FIG. 3 illustrates an example configuration 300 of induction heatingworkcoils with respect to a roll according to this disclosure. As shownin FIG. 3, the configuration 300 includes multiple induction heatingworkcoils 302 placed adjacent to each other in an end-to-end fashionacross the surface of a roll 304. The induction heating workcoils 302could have any suitable spacing, such as one induction heating workcoilevery fifty millimeters. The configuration 300 also includes multiplerows of induction heating workcoils 302. The induction heating workcoils302 in the different rows may or may not be offset, and the rows couldhave any suitable spacing.

The induction heating workcoils 302 operate to produce currents indifferent areas or zones of a conductive shell 306 of the roll 304. Theconductive shell 306 generally represents the portion of the roll 304that contacts a paper sheet or other product being formed. Theconductive shell 306 or the roll 304 could be formed from any suitablematerial(s), such as a metallic ferromagnetic material. The currentscould also be produced in different areas or zones of the roll 304itself, such as when the roll 304 is solid. The amount of currentflowing through the zones could be controlled by adjusting the amount ofenergy flowing into the coils of the induction heating workcoils 302(via control of the power sources 210). This control could, for example,be provided by the controller 104 in the paper production system 100 ofFIG. 1.

In order to reduce or minimize currents flowing through a shaft 308 andthrough bearings in a bearing house 310 of the roll 304, the inductionheating workcoils 302 are oriented so that the currents flow within theroll 304. The currents 304 are not directed parallel to the axis of theroll 304, so a reduced or minimized amount of current flows through thebearings of the roll 304.

Although FIG. 3 illustrates one example of a configuration 300 ofinduction heating workcoils with respect to a roll, various changes maybe made to FIG. 3. For example, the configuration 300 could include anynumber of rows of induction heating workcoils 302 at any uniform ornon-uniform spacing. Also, each row could include any number ofinduction heating workcoils 302 at any uniform or non-uniform spacing.

FIG. 4 illustrates an example method 400 for reducing current exiting aroll through its bearings according to this disclosure. As shown in FIG.4, one or more induction heating workcoils are placed in proximity to aroll at step 402. This could include, for example, placing multipleinduction heating workcoils 120 near a roll 119 in a paper calender. Anysuitable number of induction heating workcoils could be placed near theroll, and the induction heating workcoils could have any suitablearrangement or configuration.

The induction heating workcoils are oriented at step 404. This couldinclude, for example, orienting the induction heating workcoils so thattheir cores 206 are substantially parallel to the roll's axis. Ingeneral, the orientation involves positioning the induction heatingworkcoils so that the paths of their induced magnetic fluxes aresubstantially parallel to the roll's axis.

Once oriented, the roll can be rotated during the production of a papersheet or other continuous web product at step 406, and currents areproduced through the roll at step 408. The currents can be generated byproviding AC signals to the coils 204 of the induction heatingworkcoils. Moreover, the currents produced by the induction heatingworkcoils do not flow substantially axially within the roll, so theamount of current exiting the roll through its bearings can be reducedor minimized.

Although FIG. 4 illustrates one example of a method 400 for reducingcurrent exiting a roll through its bearings, various changes may be madeto FIG. 4. For example, while shown as a series of steps, various stepsshown in FIG. 4 could overlap, occur in parallel, occur in a differentorder, or occur multiple times.

It may be advantageous to set forth definitions of certain words andphrases used throughout this patent document. The term “couple” and itsderivatives refer to any direct or indirect communication between two ormore elements, whether or not those elements are in physical contactwith one another. The terms “include” and “comprise,” as well asderivatives thereof, mean inclusion without limitation. The term “or” isinclusive, meaning and/or. The phrases “associated with” and “associatedtherewith,”as well as derivatives thereof, may mean to include, beincluded within, interconnect with, contain, be contained within,connect to or with, couple to or with, be communicable with, cooperatewith, interleave, juxtapose, be proximate to, be bound to or with, have,have a property of, or the like. The term “controller” means any device,system, or part thereof that controls at least one operation. Acontroller may be implemented in hardware, firmware, software, or somecombination of at least two of the same. The functionality associatedwith any particular controller may be centralized or distributed,whether locally or remotely.

While this disclosure has described certain embodiments and generallyassociated methods, alterations and permutations of these embodimentsand methods will be apparent to those skilled in the art. Accordingly,the above description of example embodiments does not define orconstrain this disclosure. Other changes, substitutions, and alterationsare also possible without departing from the spirit and scope of thisdisclosure, as defined by the following claims.

1. A system comprising: a roll comprising a conductive material, theroll configured to rotate about an axis; and an induction heatingworkcoil configured to generate currents within the roll, wherein theinduction heating workcoil is unbalanced and is oriented so that minimalcurrents flow in a direction substantially parallel to the axis of theroll.
 2. The system of claim 1, wherein the induction heating workcoilcomprises: one or more substantially U-shaped or C-shaped cores; and atleast one coil, each coil wound around at least one of the one or morecores.
 3. The system of claim 1, wherein: the roll further comprises ashaft and bearings; and the induction heating workcoil is oriented sothat the currents do not flow substantially through the bearings.
 4. Thesystem of claim 1, wherein the roll comprises one of a set ofcounter-rotating rolls, the counter-rotating rolls configured tocompress a web of material.
 5. The system of claim 4, wherein: aninduction heating actuator comprises the induction heating workcoil anda power source coupled to at least one coil of the induction heatingworkcoil; and the system further comprises a controller configured tocontrol the power source to control an amount of compression provided byat least a portion of the counter-rotating rolls.
 6. The system of claim1, wherein multiple induction heating workcoils are located adjacent toeach other in a row proximate to the roll.
 7. The system of claim 6,wherein multiple rows of induction heating workcoils are locatedadjacent to each other proximate to the roll.
 8. A system comprising: aroll comprising a conductive material, the roll configured to rotateabout an axis; and an induction heating workcoil configured to generatea magnetic flux for producing currents within the roll, wherein theinduction heating workcoil is unbalanced and is oriented so that a pathof the magnetic flux through the roll is substantially parallel to theaxis of the roll.
 9. The system of claim 8, wherein the currents withinthe roll do not flow substantially parallel to the axis of the roll. 10.The system of claim 8, wherein the induction heating workcoil comprises:one or more substantially U-shaped or C-shaped cores; and at least onecoil, each coil wound around at least one of the one or more cores. 11.The system of claim 8, wherein: the roll further comprises a shaft andbearings; and the induction heating workcoil is oriented so that thecurrents do not flow substantially through the bearings.
 12. The systemof claim 8, wherein the roll comprises one of a set of counter-rotatingrolls, the counter-rotating rolls configured to compress a web ofmaterial.
 13. The system of claim 12, wherein: an induction heatingactuator comprises the induction heating workcoil and a power sourcecoupled to at least one coil of the induction heating workcoil; and thesystem further comprises a controller configured to control the powersource to control an amount of compression provided by at least aportion of the counter-rotating rolls.
 14. The system of claim 8,wherein multiple induction heating workcoils are located adjacent toeach other in a row proximate to the roll.
 15. The system of claim 14,wherein multiple rows of induction heating workcoils are locatedadjacent to each other proximate to the roll.
 16. A method comprising:placing an induction heating workcoil in proximity with a roll, the rollconfigured to rotate about an axis, the induction heating workcoilcomprising an unbalanced induction heating workcoil; orienting theinduction heating workcoil so that a magnetic flux path within the rollproduced by the unbalanced induction heating workcoil is axially alignedwith the axis of the roll; and producing currents within the roll. 17.The method of claim 16, further comprising: initially orienting theinduction heating workcoil so that the magnetic flux path is not axiallyaligned with the axis of the roll, before orienting the inductionheating workcoil so that the magnetic flux path is axially aligned withthe axis of the roll.
 18. The method of claim 16, wherein: the rollcomprises a shaft and bearings; and orienting the induction heatingworkcoil comprises orienting the induction heating workcoil so that thecurrents do not flow substantially through the bearings.
 19. The methodof claim 16, wherein the roll comprises one of a set of counter-rotatingrolls, the counter-rotating rolls configured to compress a web ofmaterial.
 20. The method of claim 19, wherein: an induction heatingactuator comprises the induction heating workcoil and a power sourcecoupled to at least one coil of the induction heating workcoil; andfurther comprising controlling the power source to control an amount ofcompression provided by at least a portion of the counter-rotatingrolls.